text: There are two main ways in which minerals hydrate. One is conversion of an oxide to a double hydroxide, as with the hydration of calcium oxide—CaO—to calcium hydroxide—Ca(OH), the other is with the incorporation of water molecules directly into the crystalline structure of a new mineral. 
  The later process is exhibited in the hydration of feldspars to clay minerals, garnet to chlorite, or kyanite to muscovite.
  Mineral hydration is also a process in the regolith that results in conversion of silicate minerals into clay minerals.
  Some mineral structures, for example, montmorillonite, are capable of including a variable amount of water without significant change to the mineral structure.
  Hydration is the mechanism by which hydraulic binders such as Portland cement develop strength. A hydraulic binder is a material that can set and harden submerged in water by forming insoluble products in a hydration reaction. The term hydraulicity or hydraulic activity is indicative of the chemical affinity of the hydration reaction.